Honeywell Thermostat Not Turning ON

The A Honeywell thermostat not turning ON can happen for many reasons. A faulty Honeywell Thermostat, a broken HVAC system, power losses, damaged wiring, et al. Here, we list some of these causes, and offer repair tips to solve these no-run issues. First, we look at what might have happened with the Honeywell Thermostat itself. Then we explore the furnace issues that can also cause no HVAC running at all.  Here, we discuss these problems, not partial-but-insufficient-heat issues.  These address the case when you get no heating or cooling. But they do not cover the cases where you get some yet not enough temperature control.

Honeywell Thermostat Not Turning ON: Possible Causes

Summary of Causes

1. 1. Honeywell Thermostat temperature offset too large.
   2. Power failure keeping HVAC unit from coming on.
   3. Honeywell Thermostat not level on wall.
   4. Temperature set too low or high.
   5. Bad electrical connections.
   6. Mechanical Honeywell Thermostats can bind up.
   7. Not set to correct operational mode (heating or cooling mode).

Honeywell Thermostat Temperature Offset Set Too High

Problem

The Honeywell Thermostat temperature display seems to show that the current room temperature never reaches the set temperature. Yet the HVAC never turns on. So in this case, the display offsets may be too high.  That is, the Honeywell Thermostat  acts as if the current indoor temperature is higher than it really is. And when the t-stat thinks that the room is warmer, it will not turn the HVAC ON.

Consider this.

• • Let’s say that you set the Honeywell Thermostat to 74 degrees.
  • Further, you have set your display temperature offset to +3 degrees. This makes your Honeywell Thermostat display a current temperature reading that is three degrees warmer than the environment actually is. In this case, when the current house temperature is 74 degrees, the Honeywell Thermostat would show 77 degrees.

Now the Honeywell Thermostat calls for HVAC when the temperature it reads drops below 74 degrees.  But a +3 degree offset means that the actual temp must fall to 3 degrees below 74 to get warmer. So though you set the temp to 74, you won’t get heat until the actual room temp falls below 71.  Now in apartment buildings, a room on the upper floors might easily hold at 71 degrees. So you may rarely or never feel the unit working if you set the Honeywell Thermostat to 74.

Fixes

Decrease the display offset temperature. This helps assure that the temp reading on the Honeywell Thermostat shows as closer to actual room temp.  Plus, an accurate display reading helps prevent the situation where your furnace does not come on enough. We suggest that you avoid setting the temperature offset to more than one degree either way (+ or – offset).

Or, just turn up the set temperature.  In this scenario, let’s say you want your place to be 74 degrees. But with the +3 degree offset, you’ll need to turn the Honeywell Thermostat higher than the temperature you desire.  So you’ll have to set it to 77 degrees to get that 74 degrees actual temperature.

Power Failure Keeps Honeywell Thermostat from Turning On the HVAC

Problem

The screen on Honeywell smart Honeywell Thermostats looks blank or dark. No readings or status messages appear. Further, the furnace does not run. Plus, you hear no humming at the furnace. But for non intelligent t-tats you may no power loss indication, except that their backlights don’t glow. Yet the effect is still the same. The HVAC Not Turning ON. That is, that the furnace never runs, no matter the Honeywell Thermostat setting.

Fixes

Honeywell thermostats often get power right from the furnace system. So, check that all furnace systems are getting electricity. Often there’s a single circuit breaker that feeds the furnace. Then there’s another that feeds the outside compressor unit in HVAC arrangements. So verify that all these breakers are ON.

Furthermore, the heating and cooling subsystems often get electricity from separate circuit breakers. So, the Honeywell Thermostat could glean power from either one, although usually not both. A power outage in either system could cause Honeywell Thermostat Not Turning ON. By checking that the HVAC control circuits have power, you’ve ruled out this cause of Honeywell Thermostat power loss. In this way, a faulty cooling system can make the HVAC system fail too.

Honeywell Thermostat Poorly Wired or Installed

Problem

If the HVAC problem happened when you installed a new Honeywell Thermostat, you may have wired it the wrong way. Perhaps you’ve reversed the W and Y wires. This would run the cooling stage though the Honeywell Thermostat is actually calling for heating. Other symptoms may arise too. These depend on which wires and how many of them you have connected to the wrong Honeywell Thermostat terminals.

Fixes

Check for correct wiring at both ends of the Honeywell Thermostat cable. At the Honeywell Thermostat, affix all wires to the right screw terminals in the mounting plate. Then, do likewise at the furnace. Seek help from a professional HVAC technician if you feel insecure matching these wires up with the right terminals.

Crooked Mounting May Cause Honeywell Thermostat Not Turning ON

Problem

Poor leveling on older Honeywell Thermostats can affect how well they respond to room temperature changes. Those early models used a bi-metal spring to sense temperature. Manufacturers would affix a mercury switch to the outside end of that spring. Then, as room temperature rose and fell, the spring changed size. This caused its outer end to move back and forth in accordance with temperature changes. This in turn tipped the mercury switch ON or OFF, to bring room temperature nearer to the set temperature.

You needed proper leveling for this tipping to occur as designed. Indeed, if tilted too far off of plum or the horizontal, the HVAC system might never turn on. In this case, the mercury inside does not make the contacts as it should when the room gets too cold.

Fixes

Now you may still have a mercury and bi-metal Honeywell Thermostat. If so, then you should replace it with a current all-electronic model that has no moving parts. Today’s Honeywell Thermostats have more accurate sensors and many more features. Plus, modern t-stats work well, no matter how far off of level you install them. They’ll turn on the furnace correctly in the house, no matter their position.  Mount them on their sides or upside down. Or, let them dangle by the wires (although we do not recommend this).  But the point is that they will regulate your heat well, in any position.

If you cannot upgrade from an older Honeywell Thermostat, then try drilling new mounting holes. To do that, remove the screws and wires if they get in the way. Then re position the Honeywell Thermostat over the new holes. Finally, drive the screws into those new holes. Use wall anchors in these holes for a stronger hold.

If your t-stat is not too far out of level, try loosening the screws that hold it to the wall. Then, slide the Honeywell Thermostat toward level. Then, mark the wall with an erasable pencil.  Next, while holding the Honeywell Thermostat in that marked position, tighten the screws again.  Finally, use an eraser to clean off any visible wall markings.

Honeywell Thermostat Temperature Set Too Low

Problem

You can set Honeywell Thermostats way lower than the ambient temperature in your home.  During moderate days outside for instance, you might set the room temperature to 72 degrees.  But if you live in a tall building, your apartment may never fall below 72 degrees.  Thus, your furnace may never come on.

Fixes

• • If you need more warmth, try setting the Honeywell Thermostat higher.
  • Or just be happy your furnace is not running any more than it is, especially if paying your own bills.

Bad Electrical Connections Might Cause Honeywell Thermostat Not Turning ON

Problem

The solid copper wires in the Honeywell Thermostat cable can break if flexed or bent too much. Or, maybe the installer stapled the cable with too much pressure, and shorted out the individual conductors in that cable.

This issue normally appears during new Honeywell Thermostat testing only. But sometimes, this problem may not show up for decades. Plus, settling of wall beams can flex these stapled wires. So, after many years, this flexing can wear wire coverings, causing faulty or no warming.

Solutions

Replace the cable between the Honeywell Thermostat and furnace. Avoid tightly stapling the wire, and don’t fasten it more than you must for a secure installation. Lay it loosely.

Mechanical Honeywell Thermostats can Bind Up

Problem

Now and then with Honeywell thermostats, static electricity near them can freeze the touch screen. Also, a power surge in the home’s electrical system can do this as well. Then too, the data shown onscreen no longer updates. Further, the HVAC system may not come on. No matter how far from set temperature the room temperature is, the furnace may not run at all.

Fixes

 

When this no run problem happens, try rebooting the Honeywell Thermostat. Turn off its power for ten to twenty seconds. Then switch it on again. This power cycling is a literal snap with many Honeywell Thermostat models. Why? Because they can detach from furnace power without having to unscrew them. Just unsnap them from wall plates. Then, wait a few seconds. And finally snap them back into place to reboot. Or, if your t-stat does not come off of the wall easily, power cycle it at the breaker box. Doing this reboots the Honeywell Thermostat.

Not Set to the Correct Operational Mode (Heating or Cooling Mode)

Problem

Certainly you might see Honeywell Thermostat Not Turning ON, when it’s not currently n heating mode!  On our smart Honeywell Thermostat,  we can set it to either heating mode, cooling mode, or OFF.  If OFF, you won’t get warmth.  Nor will any cool air flow from your registers in Cool mode.

Solution

Set the Honeywell Thermostat’s operational mode to Heat.  On our Honeywell Thermostat, we do this in the System tab. Just tap the Heat option and press Done to make the new setting effective.  You should soon thereafter feel some heating.

Other Honeywell Thermostat Posts

1. 1. How to Setup WiFi on Honeywell Thermostat
   2. Honeywell Thermostat Says Heat ON But No Heat
   3. How to Reset Honeywell Thermostat RTH9580WF
   4. How to Add Honeywell Thermostat to Google Home

References

1. 1. Official Honeywell Thermostat Support Page
   2. Where to Buy the Honeywell Thermostat